Vibrograph



Jan. 2, 1951 J, G, BURMlST 2,536,870

dnl-Mg J. G. BURMIST Jan. 2, 1951 VIBROGRAPH 2 Sheets-Sheet 2 Filed Aug. 24, 1945 FIG. 3

///////////////////////VV///// l /W FIGA! INVENTOR JOHN G. BURN!! ST *E* w24/w1 uw T. ad 3y 5 2 m WN Mw w \w\ 7///M////Q 7////-7/// m w n Patented Jan. 2, 1951 UNITED STATES snr OFFICE `andere vmRocRArn John o. surmise, Philadelphia, Pa.

Application August 24, 19,45, serai No. 612,511

(oi. zal-"71) I'CIainn;

This invention relates to vibrographs and more particularly to instruments for indicating and recording the amplitude, frequency, and charac- 4ter of vibrations of a body under test, the vibrations being resolved in three normal components, and indications thereof amplified and brought together in a single plane.

In accordance with the present invention, a vibrograph is provided, of a portable character, which is simple in its construction and reliable in its operation.

In accordance with the present invention, also, the components of vibration in normal planes are measured, indicated, and made available visually and with suitable magnification in one plane in an improved manner.

Other advantageous features will be apparent Y from the specification and claims,

The nature and characteristic features of the invention will be more readily understood from` the following description taken in connection With the accompanying drawings forming part hereof, in which: y

Figure 1 is a plan View of a vibrograph in accordance with the present invention, the housing being broken away to show the construction thereof;

Fig. 2 is a front elevational view of the Vvibograph shown in Fig. 1, with the housing broken away;

Fig. 3 is a side elevational view of the vibro,- graph shown in Fig. 1 with the housing broken away; and

Fig. 4 is a fragmentary sectional View, enlarged, showing one of the vibratory elements in detail, and taken approximately on the line A-vli of Fig. 1.

It should, of course be understood that the description and drawings herein are illustrative merely, and that various changes and modifications of the devices therein shown and described `may be made without departing from the spirit of the invention, and further, that the invention may be embodied in a variety of otherforrns not herein specically shown and described.

Referring more particularly to the drawings,

an exterior housing I0 is provided, within which the movable parts of the vibrograph are carried and protected. The upper wall of the housing |0 is provided with a slit or opening i2 and is adapted to carry thereon suitable photographic recording apparatus (not shown) for recording in one plane, indications of the components of vibrations, in the respective reference planes, of the body under test.

i kto each other, and these may be taken as indicative of X and Y components, respectively, and the mass 2&2 is restricted to act in a direction normal to the masses 22X and 22Y, and this may be taken as indicative of a Z component. `Each of the seismographic members 22X, 2QY and 222 preferably consists of a pair of blocks 2|,

.secured together in any desired manner, and

with a flat spring 22 interposed and secured therebetween. The springs 22 are respectively secured to the posts it, i5 and I6 and the distance between the blocks 2| and the posts I4, l5 and l5 is made short. The blocks 2| of the members MX and 2BY may be of the same mass and the blocks 2| of the member 202 of greater mass, the latter being subjected to the effect of the acceleration of gravity.

Pairs of spaced abutments 28 and 23 are provided on the base plate I3 and extend upwardly therefrom'on opposite sides of the seismographic members NX and 2&5? and compression springs 24 of predetermined size and spring rate or spring constant are positioned. between each of the seismographic members 28X and 2!Y and the corresponding pairs of abutments 23 and 28. An abutment plate 27 is secured to posts 25 carried by the base |3 and coil springs 25, acting in compression, are interposed between the mass 262 and the abutment plate 2l'.

Each of the seismographic systems comprising theblocks 2|, the flat springs 22 and the compression springs 243 or 28, is preferably selected and proportioned so that the blocks 2| have suitable masses` and the springs 22, 24 and 25 `have suitable spring rates or spring constants to provide the desired natural period of oscillation of the respective systems. The spring rate or spring constant is the characteristic of a spring which is measured by the load necessary to produce., a unit extension or compression of the spring. The effect of the springs 22 is relatively small, their purposes being primarily to provide a frictionless sup-port and to restrict the action of the masses ZQX, ZY and 292 to the desired direction and in the desired plane.

The natural period of oscillation of these systems is preferably considerably below the range of the vibrations to be studied, measured, and indicated or recorded. With a system having a natural period of vibration `of the order of 202 oscillations per minute the instrument will be satisfactory for a range of the order of 450 to 25,000 oscillations per minute.

The base E3 is provided with a pair of posts on which a horizontal spindle plate 3l is mounted. The plate 3| has pairs of upstanding brackets 32X, 32Y and 322 in which jewels 33 are mounted to provide bearings for parallel spindles 34X, 34Y and 342.

The mass 20X is c-onnected to the spindle 34X for actuating the same, and for this purpose a suitable connector 35X, which may consist of a wire of stainless steel of a cord of silk or rayon is provided. The connector 35X preferably extends irom an adjustable Stud 36X carried by the mass 20X, beneath a roller 3l, mounted in a downwardly extending bracket 38 carried by the spindle plate 3 l then upwardly through an opening 3 la in the spindle plate 3 I, around the spindle 34X and to a tension spring 39X carried on a bracket 40 secured to the spindle plate 3 l.

The mass 29Y is connected to the spindle 34Y for actuating the same, and for this purpose a connector 35Y is provided. The connector 35`SZr is carried by an adjustable stud SBY mounted in the mass 20Y and extends to and around the spindle 343 and to a tension spring 39Y carried by a post 4l on the bracket 40.

The mass 202 is connected to tlie spindle 342 for actuating the same and the connector 352 extends from an adjustable stud 332, to and around the spindle 3&2, and to a tension spring 392 carried by a bracket 402 which extends upwardly from and is carried by, the spindle plate 30.

Each of the spindles 34X, 34Y` and 342 is provided with a mirror X, 45Y and 452, respectively, preferably convex, for reecting light from a suitable source 46, which preferably includes an'electric lamp having aline filament, for rele'ction to Vthe opening l2 for recording by the photographic apparatus or for visual observation.

i In order to .provide a suitable adjustment for Vzero setting of the mirrors 45X, and 45Y, a rod is provided for each of the masses 20X and 20Y extending between the corresponding pairs of posts 23 and 28. The rods 50 are adapted for sliding movement in the posts 28 and 23 at the inner ends thereof, and the outer ends are slotted as at 5l for adjustment and are in threaded engagement with the outer posts 28 and 23. The rods 50 have threaded thereon spring abutments 52 which are adapted to be adjusted longitudinally on the rods for adjustment and equalization of the force exerted by the springs 24. The spring abutments 52 have sleeves 53 extending into the ends of the springs 24. The rods 50 with the springs 24 in adjusted position may be moved by turning the same with a screwdriver in the end slots 5i to position the springs 24 and the masses 20X and ZBY therebetween to give the desired positioning of the mirrors 45X and 45Y.

The spring abutments 522 for adjusting the springs 25 preferably have threaded extensions 54 in engagement with the abutment 'plate 21.

' vestigate vibrations.

The spring abutments 522 have end slots 55 for turning the spring abutments 522 to adjust the springs 26.

With the mirrors 45X, 45Y, and 452 adjusted to their zero positions, the vibrograph is positi-oned at the location where it is desired to in- Upon being subjected to vibrations, a relative movement is eiected between the base i0 and the seismographic masses 20X, 20Y, and 202. The respective linear components of movement are transmitted through the connectors 35X, 35Y, and 352 to the respective spindles 34X, 34Y, and 342 and the light picked up by the mirrors 45X, 45Y, and 452 from the light source 46 is reflected to the opening l2 for recording. The amplication of these linear components is effected by the use of the spindles 34 and the mirrors 45 and the spacing of the same from the opening l2. Each of the indications from the respective reference planes will be of equal intensity. The visible indication or 'record obtained in the photographic recording apparatus (not shown) may then be investigated in the usual manner to ascertain the amplitude, frequency, wave-form, and phase relationship of the respective components.

I claim:

In a vibrograph, an oscillatory system comprising a seismographic mass, a at resilient member to which said mass is secured at one end, and additional resilient members, in combination with a base, a support for said flat resilient member secured to said base and to which the other end of the nat resilient member is rigidly secured for determining the plane of movement of the mass, a xedly `mounted abutment member secured to said base and intersecting the plane of movement of said mass, Van adjustable supporting rod in screw threaded engagement with said 'abutment member and disposed in the plane of Vmovement of said mass, said rod being movable Vlalong its longitudinal axis in said abutment member and extending through an opening in said mass, spaced holding members in threaded engagement with said supporting rod on opposite sides of said mass, said additional resilient members being mounted on said supporting rod in yengagement with said holding members and with Yopposite sides of said mass, the natural period of oscillation of said oscillatory system being de'- termined by the mass and by the spring constants of said resilient members.

` JOHN G. BURMIST.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENT 

